The present invention relates to a balloon catheter suitably used as for example a balloon catheter for dilatation of blood vessels, more particularly relates to an improvement of a balloon catheter of a so-called monorail type.
In recent years, the trend in medical technology has been toward less invasive treatment. For example, stenosis of the coronary artery is increasingly being treated by vasodilation balloon catheters instead of the former coronary bypass surgery. This method of treatment has both economic advantages and lightens the load on the patient, so is increasingly growing in application. Along with this, balloon catheters are being required to be structured to enable dilatation of stenosis portions of the coronary artery more efficiently and simply than ever before.
As a method for treating stenosis portions in blood vessels, percutaneous transluminal coronary angioplasty (PTCA) is known. In this method, a balloon catheter is inserted into a blood vessel and the balloon unit is inflated so as to dilate the stenosis portion and thereby improve the flow of blood at the terminal side of the stenosis portion. As a balloon catheter used for this PTCA, there are an over-the-wire type balloon catheter and monorail type balloon catheter. In these types of balloon catheters, first the guidewire is made to pass through the stenosis portion in the blood vessel, then the balloon catheter is fed along the guidewire to the stenosis portion and the balloon unit inflated to dilate the stenosis portion. The stenosis portion must be dilated in stages so as not to damage the blood vessel. First, a balloon catheter with a small outside diameter balloon unit is inserted along the guidewire and then is exchanged with balloon catheters having successively larger outside diameter balloon units.
The over-the-wire type balloon catheter has a guidewire lumen formed over the entire length of the catheter tube. The guidewire is inserted along the lumen. The balloon unit is guided to the stenosis portion along this guidewire. After the dilatation of a blood vessel by a balloon catheter having a small outside diameter balloon unit, this is exchanged with a balloon catheter having a larger outside diameter balloon unit. At this time, the balloon catheter is pulled out along the guidewire, so the proximal end of the guidewire has to extend outside the body by at least the entire length of the catheter tube. If not, it is not possible to exchange a balloon catheter while leaving the distal end of the guidewire in the stenosis portion.
As opposed to this, in the monorail type balloon catheters disclosed in Japanese Unexamined Patent Publication (Kokai) No. 63-288167, U.S. Pat. No. 4,762,129, U.S. Pat. No. 5,061,273, or Japanese Unexamined Patent Publication (Kokai) No. 9-276411, an opening is formed in the middle of the catheter tube and a guidewire is guided from the opening through a guidewire insertion lumen to the distal end of the balloon unit. Due to this, in this type of balloon catheter, the length of the guidewire extending outside of the body for exchange of balloon catheters need only be slightly longer than the length from the opening to the distal end of the balloon. In this type, since the length of the guidewire can be shortened compared with the other type, the operability is excellent.
In the balloon catheters disclosed in the above publications, however, compared with the over-the-wire type, there was the problem of difficulty of insertion of the catheter into the blood vessel. As a method for dealing with this problem, a catheter tube where the distal end and proximal end of the catheter tube are comprised using different materials with different hardnesses and modulii of elasticity and these are joined to give a distal end with flexibility and a proximal end with rigidity has been reported. In this structure of a catheter tube, however, since the hardness changes sharply at the joined portion of the different materials, it is difficult to say that the operability is ideal. Further, since it is difficult to finish the joined portion completely smoothly, the catheter becomes difficult to insert into the blood vessel.
In the balloon catheter disclosed in U.S. Pat. No. 4,762,129, a dilatation use tubular member formed with a balloon inflation lumen and a wire use tubular member formed with a guidewire insertion lumen overlap over a predetermined distance along the axial direction. At the overlapped portion, the proximal end neck portion of the balloon unit is joined to cover part of the overlapped portion. In the balloon catheter disclosed in this publication, however, the outside diameter of the dilatation use tubular member becomes remarkably thinner compared with the portion overlapping the wire use tubular member, so there is the problem that kinks tend to occur.
Further, in the balloon catheter disclosed in U.S. Pat. No. 5,061,273, the dilatation use tubular member formed with the balloon inflation lumen and the wire use tubular member formed with the guidewire insertion lumen are overlapped across a predetermined distance along the axial direction at a position closer to the proximal end side than the proximal end of the balloon unit. Therefore, the outside diameter of the overlapped portion becomes larger and there is difficulty in the insertability of the balloon catheter. If the outside diameter of the dilatation use tubular member closer to the proximal end side than the overlapped portion is made smaller so as to reduce the outside diameter of the overlapped portion, there is also the problem that kinks tend to occur. Further, it is not possible to improve the strength of the proximal end neck portion of the balloon unit.
Further, in the balloon unit disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-276411, the ends of the two tubular members comprising the catheter tube are covered by separate tubular members, the outside diameters of those portions have thick step portions and there is difficulty in the insertability of the balloon catheter.
Further, in the technology disclosed in this publication, it is not possible to improve the strength of the proximal end neck portion of the balloon unit.
The present invention was made in consideration of this actual situation and has as its object the provision of a balloon catheter which is superior in insertability of the balloon catheter, improves the strength of the proximal end neck portion of the balloon unit, and is superior in resisting kinking.
To achieve the above object, the balloon catheter of the present invention comprises
a first tubular member in which at least one balloon lumen is formed inside along a longitudinal direction thereof;
a balloon unit which is communicated internally with the balloon lumen formed in the first tubular member and capable of being expanded by a fluid fed through that balloon lumen; and
a second tubular member extending axially inside the balloon unit and provided axially therein with at least one guidewire lumen;
a distal end of the balloon unit connected with a distal end of the second tubular member;
an overlapped portion formed by overlapping a proximal end of said second tubular member with a distal end of said first tubular member axially over a predetermined distance;
a neck portion of a proximal end side of said balloon unit directly or indirectly connected with at least part of said overlapped portion so as to cover at least part of said overlapped portion; and
a portion of an outside diameter smaller than an outside diameter of a proximal end of the first tubular member, which is formed on the distal end of said first tubular member.
That is, the balloon c at hater of the present invention has as its object to keep the increase of the outside diameter of the overlapped portion the minimum necessary, to prevent the outside diameter of that portion from becoming thicker in sharp increments, and to improve the insertability of the balloon catheter in a blood vessel etc. and is characterized by having a portion with an outside diameter smaller than the outside diameter of a proximal end of the first tubular member, which is formed on the distal end of the first tubular member.
The balloon catheter according to a first aspect of the present invention comprises
a first tubular member in which at least one balloon lumen is formed inside along a longitudinal direction thereof;
a balloon unit which is communicated internally with the balloon lumen formed in the first tubular member and capable of being expanded by a fluid fed through that balloon lumen;
a second tubular member extending axially inside the balloon unit and provided axially therein with at least one guidewire lumen;
a distal end of the balloon unit connected with a distal end of said second tubular member;
an overlapped portion formed by overlapping a proximal end of said second tubular member with a distal end of said first tubular member axially over a predetermined distance;
a neck portion of a proximal end side of said balloon unit directly or indirectly connected with at least part of said overlapped portion so as to cover at least part of said overlapped portion; and
a recess in which a part of an outer circumference of the proximal end of the second tubular member is received and which is formed axially on an outer circumference of the distal end of said first tubular member.
A balloon catheter according to a second aspect of the present invention comprises
a first tubular member in which at least one balloon lumen is formed inside along a longitudinal direction thereof;
a balloon unit which is communicated internally with the balloon lumen formed in the first tubular member and capable of being expanded by a fluid fed through that balloon lumen; and
a second tubular member extending axially inside the balloon unit and provided axially therein with at least one guidewire lumen;
a distal end of the balloon unit connected with a distal end of said second tubular member;
an overlapped portion formed by overlapping a proximal end of said second tubular member with a distal end of said first tubular member axially over a predetermined distance;
a neck portion of a proximal end side of said balloon unit directly or indirectly connected with at least part of said overlapped portion so as to cover at least part of said overlapped portion; and
a tapered portion where the outside diameter becomes smaller toward the distal end of the first tubular member, which is formed on at least a part of said first tubular member.
The second tubular member preferably has at least partially a tapered portion where the outside diameter becomes smaller toward the proximal end of the second tubular member.
The length of the overlapped portion is not particularly limited, but preferably is 2 mm to 500 mm. If the length of the overlapped portion is too short, the strength of the joined portion of the tubular members tends to become insufficient, while if too long, the material is wasted.
The axial length of the proximal end neck portion of the balloon unit may be longer or shorter than the axial length of the overlapped portion, but is preferably longer. If the neck portion is too long, however, the material is wasted, so the length is preferably not more than 500 mm. The reason why the neck portion is preferably longer than the length of the overlapped portion is that by configuring the balloon catheter in this way, the step portion where the outside diameter changes in the overlapped portion becomes positioned inside the neck portion. Due to this, the insertability of the balloon catheter is further improved.
The recess is preferably formed by making part of the outer circumference of the distal end of the first tubular member deform along the axial direction. By forming the recess by making the distal end of the tubular member deform, the mechanical strength of the distal end of the tubular member is increased.
The axial length of the recess is preferably longer than the length of the overlapped portion. Further, in the second aspect of the present invention, the axial length of the tapered portion where the outside diameter becomes smaller toward the distal end of the first tubular member preferably is longer than the length of the overlapped portion. By configuring the balloon unit in this way, the mechanical strength between the neck portion and the tubular member at the proximal end side from the neck portion can be improved without making the outside diameter of the axial direction overlapped portion too thick. Further, it becomes easy to take out the guidewire from the proximal end opening of the guidewire lumen formed in the second tubular member.
Further, the proximal end opening of the guidewire lumen formed in the second tubular member is preferably an inclined opening obtained by cutting the end of the tubular member at a slant angle. It becomes easy to take out the guidewire from the slanted opening.
The first tubular member and the second tubular member may be made the same material, but preferably are made of different materials. For example, the second tubular member is preferably configured by a material superior in flexibility (including xe2x80x9cpliabilityxe2x80x9d) compared with the first tubular member. Alternatively, the material of the first tubular member is preferably a material of a higher hardness than the second tubular member. By configuring the invention in this way, the flexibility of the balloon catheter is improved at the distal end side and therefore the insertability of the balloon catheter into a blood vessel etc. is improved. Further, the outside diameter of the second tubular member is preferably smaller than a reference outside diameter of the first tubular member. By configuring the invention in this way, the flexibility of the second tubular member is improved compared with the first tubular member. When forming the recess at the distal end of the first tubular member, the xe2x80x9creference outside diameterxe2x80x9d means the outside diameter of the portion where the recess is not formed, while when forming a taper, it means the maximum outside diameter.
As the means for joining the first tubular member and the second tubular member, it is possible to use the means such as adhesion, heat bonding, etc. As the means for directly or indirectly joining the proximal end neck portion of the balloon unit to at least part of the overlapped portion from the outside, it is possible to use the means such as adhesion, heat bonding, or heat bonding using a heat shrink tube.
When a clearance arises between the tubular member and the proximal end neck portion of the balloon unit, the clearance may be filled with an adhesive, sealant, or other filler.
It is possible to wrap a reinforcing wire at least at part of the outer circumference of the overlapped portion and cover the outer circumference of this with the proximal end neck portion of the balloon unit and join the same. By using a reinforcing wire, joining different or similar tubular members which are difficult to adhere or fuse together becomes easy.
The proximal end neck portion of the balloon unit may have an inside diameter which is constant along the axial direction, but it is also possible to form it into a taper where the inside diameter becomes larger toward the proximal end side. If forming the taper, covering the neck portion over the overlapped portion becomes easy and the work efficiency is improved when producing the balloon catheter.
In the balloon catheter according to the first aspect of the present invention, the outer circumference of the distal end of the first tubular member is formed along the axial direction with a recess into which part of the outer circumference of the proximal end of the second tubular member fits. Therefore, the outside diameter of the overlapped portion between the distal end of the first tubular member and the proximal end of the second tubular member can be kept to the minimum necessary. Further, since the tubular members are joined in the proximal end neck portion of the balloon unit, a step of the joint portion is made small and the balloon catheter can be easily inserted into a blood vessel etc. Further, since the first tubular member and the second tubular member are joined at the overlapped portion, even tubular members comprised of materials difficult to adhere or heat bond together can be easily joined and there is little sharp change in hardness along the longitudinal direction.
Further, by joining the proximal end neck portion of the balloon unit so as to cover at least part of the overlapped portion, the strength of the neck portion is improved.
Further, the recess is formed at only the distal end of the first tubular member. The recess is not formed at other portions. It is therefore possible to sufficiently increase the sectional area of the flow channel of the balloon lumen formed at the first tubular member and possible to reduce the flow resistance of the lumen. Still further, at the portion where no recess is formed, it is possible to sufficiently increase the outside diameter or thickness of the first tubular member and possible to effectively prevent kinks. Further, the pushability (stiffness) of the balloon catheter is also excellent. Note that in order to further improve the mechanical strength of the first tubular member, a reinforcing wire (for example, a metal wire) may be arranged inside in the longitudinal direction or a reinforcing fiber may be braided.
In the balloon catheter according to the second aspect of the present invention, the distal end of the first tubular member has at least partially a tapered portion where the outside diameter becomes smaller toward the distal end of the first tubular member. Therefore, the outer diameter of the overlapped portion between the distal end of the first tubular member and the proximal end of the second tubular member can be kept to the minimum necessary. Further, since the tubular members are joined together in the proximal end neck portion of the balloon unit, a step of the joint portion is made small and the insertability of the balloon catheter into a blood vessel etc. is improved.
Further, since the first tubular member and the second tubular member are joined at the overlapped portion, even tubular members comprised of materials difficult to adhere or heat bond together can be easily joined and there is little sharp change in hardness along the longitudinal direction.
Further, by joining the proximal end neck portion of the balloon unit so as to cover at least part of the overlapped portion, the strength of the neck portion is improved.
Further, since there is a tapered portion where the outside diameter becomes smaller toward the distal end of the first tubular member, the portion where the sectional area of the flow channel of the balloon lumen formed at the first tubular member becomes smaller can be kept to the minimum necessary and the flow resistance of the lumen can be reduced. Still further, at the proximal end side closer than the tapered portion formed at the distal end of the first tubular member, it is possible to sufficiently increase the outside diameter or thickness of the first tubular member and possible to effectively prevent the first tubular member from kinking. Further, the pushability of the balloon catheter is also excellent. Note that in order to further improve the mechanical strength of the first tubular member, a reinforcing wire (for example, a metal wire) may be arranged inside in the longitudinal direction or a reinforcing fiber may be braided.